Classic American EQ.


AQ550b 4-Band Equalizer

Based on Classic American EQ from the late ’60s, the AQ550b is a continuation of the EQ
that played a major role in the history of music recording, but with an additional filter band
and several new frequencies. With a surprisingly wide range of tonal variations, the AQ550b
is an invaluable and professional audio tool with great flexibility and excellent sonic ability.

Rather than offer a huge assortment of complex features, the AQ550b provides exactly the
right number of controls. Its four EQ bands are overlapped significantly to aid in dual roles as
problem solver and sweetening device with each band offering seven switchable filter
frequencies that span four-to-five octaves. These frequencies, purposely selected to be
musical rather than numeric.

Making use of Proportional Q intuitively widens the filter bandwidth at minimal settings and
narrows it at higher settings without the need for additional bandwidth controls. This unique
feature minimizes the «phase-shift» sound found in many equalizers.

The AQ550b extends the features of the original hardware and joins the flexibility of the
digital world to the character of the analog processing. The AQ550b plugin designed from the
ground up for fast, efficient work on mid/side, stereo and the objects, the beds (fixed
channels) of immersive mixing environments.

Surround profiles do not work correctly in Logic Pro, this is due to a bug in Logic Pro compatibility with AUv3 on multi-channel tracks (When Apple fixes this, our plugin will work correctly). AUv3 on multi-channel tracks works absolutely right in Reaper.

Latest Versions

AUv3 version 3.0.0 (Jun 27, 2023)
VST2 version 3.0.0 (Jun 27, 2023)
VST3 version 3.0.0 (Jun 27, 2023)

VST2 version 3.0.0 (Jun 27, 2023)
VST3 version 3.0.0 (Jun 27, 2023)


USD 79
USD 29



Fx Selection

This module allows you to select a equalizer from four available. The equalizers are arranged in series, this allows you to process channels with different equalizers settings. For example: the first EQ is only the mid channel, the second EQ is only the side channel, the third Eq is the left and right channel. For multi-channel modes: the first Eq is only the left and right channels, the second EQ is the center channel, the third EQ is the LFE, etc.
You can rename Fx Buttons for ease of use. To rename the selected Fx button, right-click on the button.
In order to turn on the solo (listen) of the equalizer, double-click on the selected equalizer number. The equalizer in solo mode glows yellow, to exit solo mode, double-click again. For two-channel modes, only one equalizer can be solo mode. For multi-channel modes, one or more equalizers can be soloed.
To bypass Eq processing, press the selected equalizer number one click + shift. In bypass mode, the button will glow red.
You can also copy all equalizer settings to another equalizer. To do this, select the equalizer from which you want to copy the settings, then click on the copy button, then select the equalizer to which you want to copy the settings.

Input Routing
Input Routing lets you choose between 44 common channel setups, starting from Stereo up to 7.1.4 and 9.1.6. Simply select in the input routing module the channel setup that fits your track.
You can also create your own input routing profiles. 16 independent channels are available.
Click on the edit button next to the input routing selection display. Hold down the shift button and select the desired number of channels. Name selected channels in order. Then click save and name the profile.

Channels Selection
In this module, you can select (activate) the channels that the equalizer will process.



Low Frequency (LF)

Low Band Frequency
Filter types: Shelf, Bell
Default: Bell
Range: 30Hz, 40Hz, 50Hz, 100Hz, 200Hz, 300Hz, 400Hz

Low Band Gain
Range: -12dB to +12dB

Low Mid Frequency (LMF)

Low Mid Band Frequency
Range: 75Hz, 150Hz, 180Hz, 240Hz, 500Hz, 700Hz, 1kHz
Filter types: Bell

Low Mid Band Gain
Range: -12dB to +12dB

High Mid Frequency (HMF)

High Mid Band Frequency
Range: 800Hz, 1.5kHz, 3kHz, 5kHz, 8kHz, 10kHz, 12.5kHz
Filter types: Bell

High Mid Band Gain
Range: -12dB to +12dB

High Frequency (HF)

High Band Frequency
Filter types: Shelf, Bell
Default: Bell
Range: 2.5kHz, 5kHz, 7kHz, 10kHz, 12.5kHz, 15kHz, 20kHz.

High Band Gain
Range: -12dB to +12dB

Bell/Shelf Switches

The LF and HF bands are normally in bell mode. When the Bell/Shelf switch is engaged for
the band (in the down position), the band is switched to shelving mode.

LF Shelf
When the LF Shelf switch is engaged, the low frequency band is switched to shelving mode.

HF Shelf
When the HF Shelf switch is engaged, the high frequency band is switched to shelving mode.




This knob controls the level of harmonics added to the signal. The distortion is mild and adds some coloration.

Switches between the old and new revision equalizer emulations.

Phase (Polarity)
Shifts the phase by 180 degrees.

The EQ is active when the EQ IN button is engaged and its associated LED is illuminated. When this button is off, selected EQ is disabled. Please note that this button disables only the selected equalizer, the rest of the equalizers in the FX blocks are not disabled.

Output Gain
This knob is an output gain control. The available output gain range is ±24 dB.


Comp609 4


Undo and Redo functions allow undo and redo of changes made to the plug-in parameters.

A/B buttons allows you to load two independent settings and compare them quickly.

Preset Display
Factory presets are included in the plug-in installation, installed in the following locations:
Mac: Users\[user name]\Music\Red Rock Sound\RRS AQ550b\Patches
Windows: C:\Users\[user name]\Documents\Red Rock Sound\RRS AQ550b
You can save the current Comp settings as the Default preset. - Full Reset – is the default preset
Load button allows loading of presets not stored in the locations described above.
Save button allows for save of user presets.

Global Output Gain
Global Output Gain controls the overall output level of the plug-in output, after all equalizers.

OS x_ activates 2x, 4x or 8x oversampling, 1x disables oversampling. (note that when the HQ mode is on, CPU will be loaded more than usual).

HQ mode (HQ)
HQ mode is for oversampling, it adds a higher order antialiasing filter. It improves processing quality, but also leads to an increase of the CPU load.

? button opens info page.

D3D / OGL / CPU (Windows)
This switch allows you to choose between GUI rendering engine:
Normally, no need in switching rendering mode manually, plug-in try to initialize D3D9 then OGL (if D3D9 failed) and CPU (if OGL failed) automatically. But if you have problems with the GUI, you can manually switch and test different rendering methods at work.

This switch is available only in the Windows version of the plugin. For the Mac version, this is not necessary.

Note: Drivers of some video cards (for example, Intel Arc A380) in D3D mode adversely affect the plug-in (periodic noise or whistle), if you encounter a similar phenomenon, use OGL or CPU.

SIMD optimization
This switch enables or disables SIMD optimization, it can be used by multichannel processing with high oversampling. It is undesirable to use in mono and stereo modes, SIMD only slows down the plug-in due to the overhead of splitting the data for optimization.
(Currently in beta testing)

- In the ARM version, you can enable or disable NEON; - In the Intel version, you can enable or disable SSE2.

SIMD Windows
- In the Intel version, you can enable or disable AVX (if supported), or SSE2.

The Windows version has a limitation: if the CPU does not support FMA, then the optimization will not work, even if AVX or SSE2 is supported.

Note: Enabling/disabling SIMD is saved in the project for each plugin individually. i.e. if a specific instance of the plugin slows down, then you can enable SIMD for it, and others, if they are in the project, will not be affected by this optimization.